Non-corrosive regular packing member and a method of making same

ABSTRACT

A non-self-supporting base material of glass fibers is first formed and then coated by an ionotropic sol to have a hard coating formed on the glass fibers. The coating is made of a bonding agent containing at least one glass-forming oxide selected from the compounds of silicon, aluminum, zirconium and titanium. The stiffened structure is useful in any shape for a regular packing such as in layer form, honeycomb and the like.

United States Patent Grochol et a1,

NON-CORROSIVE REGULAR PACKING MEMBER AND A METHOD OF MAKING SAMEInventors: Jan Grochol, Winterthur; Werner Meier, Elgg, both ofSwitzerland Assignee: Sulzer Brothers Limited,

Winterthur, Switzerland 7 Filed: May 16, 1974 Appl. No.: 470,446

Foreign Application Priority Data May 23, 1973 Switzerland 7304/73 US.Cl. 264/129; 55/521; 55/524; 65/3; 261/D1G. 72; 264/257; 427/372;428/182; 428/228; 428/289; 428/392 Int. B29H 9/02; B32B 17/02 Field ofSearch....... 161/89, 93, 133, 135, 170, 161/D1G. 4; 264/58, 257, 280,129, 134; 261/D1G. 72, 108, 112; 117/126 GF;

156/178, 181; 55/521, 524, 527, DIG. 16; 428/392, 182, 184; 65/3, 4

[ Dec. 16, 1975 [56] References Cited UNITED STATES PATENTS 3,801,4194/1974 Meek 1. 161/133 Primary Examiner-George F. Lesmes AssistantExaminer-Paul J. Thibodeau Attorney, Agent, or Firml(enyon & KenyonReilly Carr & Chapin [57] ABSTRACT A non-self-supporting base materialof glass fibers is first formed and then coated by an ionotropic sol tohave a hard coating formed on the glass fibers. The coating is made of abonding agent containing at least one glass-forming oxide selected fromthe compounds of silicon, aluminum, zirconium and titanium. Thestiffened structure is useful in any shape for a regular packing such asin layer form, honeycomb and the like.

3 Claims, 6 Drawing Figures Sheet 1 of2 US. Patent Dec. 16, 1975 U.S.Patent Dec. 16, 1975 Sheet2of2 3,927,165

NON-CORROSIVE REGULAR PACKING MEMBER AND A METHOD OF MAKING SAME Thisinvention relates to a non-corrosive regular packing member and to amethod of making the same.

Heretofore, it has been known to make column components from materialssuch as metal alloys, porcelain, asbestos and plastics for materialexchange columns such as are used for distillation, rectification,absorption, regeneration and extraction operations; for wetting anddrying; for performing chemical reactions; and for heat exchangers whichare used, for instance, in air conditioning to cool or heat one agent bymeans of a heat exchange agent. Generally, these column components arerequired to have very large surface areas, and depending on whether thesurface areas are regular or irregular, the corresponding columncomponent is known as either a regular packing or a statistical packmg.

However, statistical packings are unsatisfactory for many processes,such as the rectification of temperature-sensitive substances, since theconsiderable pressure drop arising in such packings may lead to a hightemperature at the bottom of the column and, hence, to decomposition ofthe treatment products. Low pressure drops are important too inabsorption processes, for instance, in a waste air cleaningprocess, soas to bring about a considerable reduction in the power required tooperate the fans for moving the waste air. Consequently, it is perferredin all such processes to use regular packings, for which the pressuredrop is less than for statistical packings.

Generally, the regular packings which are the most common at the presenttime are prepared from a woven or knitted fabric of metal wires. Otherknown regular packings are devised from asbestos or plastics. The wovenor knitted metal items are mostly prepared from narrow wires.Unfortunately, these wires which are usually made of steel, are notcorrosion-resistant to a large number of substances which have to betreated.

Asbestos members can withstand a relatively large number of substancesbut must be of relatively large wall thickness, since asbestos is sobrittle. The resulting regular packing elements are, therefore, heavyand the free space or gap volume for a given diameter is reduced, sothat the pressure drop increases.

It has already been suggested to form layers of regular-packing membersof asbestos paper with the layers being treated with a non-shrinksynthetic resin such as epoxy or phenol resin. Unfortunately, resins ofthis kind can only withstand temperatures of, at most, approximately lCand are therefore of use for only a limited number of processes.

Plastics regular-packing members also have the disadvantage of beingusable only at relatively low temperatures, and so their range ofapplication is fairly narrow. These packing members also have thedisadvantage that their pore wettability leads to poor liquiddistribution, since pooling occurs, so that there is a reduction in thesuperficial area available for material for heat exchange.

In another known form of regular packing members which have satisfactoryliquid distribution over the whole cross-section of a single member, theconstruction is in the form of fluted or corrugated strips of a knittedor woven fabric of textile or glass fibers, the dimensional stability ofthe articles being increased by 2. the provision at intervals of metalwires. However, the stiffening metal wires are disadvantageous, sincefor manufacturing reasons the wires must be narrow and, thus are likelyto be destroyed by corrosion.

Accordingly, it is an object of the invention to provide a regularpacking member which is corrison-resistant.

It is another object of the invention to form a regular packing memberwhich is temperature resistant over a temperature range in whichmaterial exchange or heat exchange processes occur.

It is another object of the invention to provide a regular packingmember which can be used for temperatures up to 300C.

It is another object of the invention to provide a re gular packingmember which is wettable for treating organic and inorganic liquids.

Briefly, the invention provides a regular packing member having anon-self-supporting base material of glass fibers and a coating of abonding agent containing at least one glass-forming ingredient on thefibers. The bonding agent serves to join the individual glass fiberstogether. The bonding of the glass fibers together serves to stiffen thebase material so that the base material becomes dimensionally stable.

The glass-forming oxide is selected from compounds of silicon, aluminum,zirconium and titanium. The coated base material serves to form walls todefine flow channels. For example, shaped layers of the base materialcan be placed together to form a packing member having a multitude offlow channels, e.g. arranged in a criss-crossing pattern.

The invention also provides a method of making a regular packing membercomprising the steps of wetting a flat structure of glass fibers with anionotropic sol and of thereafter drying the wetted structure at atemperature of 300C or less to chemically bond a solid coating to theglass fibers and form a stiffened structure. The wetted structure isshaped prior to being dried into the stiffened structure in order toform the packing member.

The term ionotropic sol denotes a sol which consists of chargedcolloidal particles and which sol in the cme of the invention containsglass-forming components which enter into a chemical compound with theglass fibers.

The term non-self-supporting base material of the glass fibers isintended to denote a woven fabric of glass fiber bunches or a knittedfabric or a fleece having open loops.

The regular packing member is not limited to any particular structure.For instance, the regular packing member may be in the form of fluted orcorrugated layers which are brought together. A regular packing membercan also, if required, have a honeycomb structure, the flow channelcross-sections being polygonal, e. g. square or hexagonal in shape. Ifrequired, the structure can take the form of a fluted or corrugatedcoiled strip.

A typical exemplary use of regular packing members made of glass fibersis in the rectification of temperature-sensitive high-boiling-pointcompounds containing chlorine or bromine. Because of a tendency todecompose, substances of this kind must be rectified in vacuo,

and for this purpose it is preferred to use regular packings which areassociated with a reduced pressure drop. The decomposition products ofsuch compounds are highly corrosive and make it impossible to usestainless steel wires.

Another use is in the rectification of dicarboxylic acids wherein asevere corrosive action makes it necessary, for instance, to usetitanium. Unfortunately, titanium is very costly, particularly because,in normal exchange processes, a large number of regular packing memberswhich are of relatively large diameter have to be used. However, regularpacking members according to the invention are much cheaper and areresistant to corrosion by dicarboxylic acids.

Another example is in the rectification of some organic products forwhich rectification is usually given at an elevated temperature of e.g.150C or more. In such cases, regular packing members made of plasticscould not be used, nor could metal members, for in this case the treatedproducts would decompose catalytically in contact with metals.

The invention allows the discrete glass fibers to be covered by a thinglassy layer which has been evolved from a colloidal solution. The layerbonds the discrete fibers together, the fiber structure being retainedas such while most of the loops present before application of the solremain open after treatment, thus ensuring a satisfactory materialexchange between adjacent flow channels.

These and other objects and advantages of the invention will become moreapparent from the following detailed description and appended claimstaken in conjunction with the accompanying drawings in which:

FIG. 1a illustrates a longitudinal sectional view of part of a fiberbunch or group which has been stifiened or reinforced in accordance withthe invention;

FIG. lb illustrates a cross-sectional view taken on line Ib-Ib of FIG.1;

FIG. 2 illustrates a cross-sectional view similar to FIG. 112, through alarger portion of a coated glass fiber bunch;

FIG. 3 diagrammatically illustrates part of a glassfiber woven fabricwhich has been coated in accordance with the invention;

FIG. 4 diagrammatically illustrates a regilar packing member accordingto the invention for use for a crosscurrent heat exchanger; and

FIG. 5 diagrammatically illustrates a number of discrete layers of aregular packing member according to the invention for a crylindn'calcross-section material exchange column.

Referring to FIGS. 1a and lb and 2, glass fibers l of a diametereg. of 5and 12 microns (,u.) and forming part of a group -or bunch are coveredby a glass-like.

layer 2 which has bonded chemically with the glass fiber surfaces. Thefibers 1, before being coated, form a non-self-supporting base material.

The coated glass fibers l have gaps 3 defined between various randomfibers to ensure satisfactory capillary action within each individualbunch of glass fibers. This ensures that the liquids to be treated aredistributed uniformly during a material or heat exchange process.

The coated glass fibers 1 also have junctions between adjacent glassfibers which are produced during coating. These junctions serve tostiffen the base material.

Referring to FIG. 3, bunches of glass fibers 4 forming the warp and weftyarns are woven into a fabric and thereafter coated. As shown, aftercoating of the fabric, open loops 5 remain so that the liquid to betreated in the material or heat exchange process can flow through theopen loops 5. During use, liquid layers can arise on 4 both sides of theloops 5 and are important in the exchange of material or heat. Liquidcan, therefore, be conveyed from any layer of a regular packing memberto the immediately adjacent layer.

Referring to FIG. 4, a regular packing member is made up of a pluralityof discrete layers 6, 7, each of which is formed, as above, of a wovenor knitted fabric or fleece of coated glass fibers. The layers 6, 7 havewalls which define flow channels, each wall including anon-self-supporting base material of glass fibers and a coating of abonding agent containing at least one glassforming oxide selected fromthe compounds of silicon, aluminum, zirconium and titanium. The packingmember is useable in a cross-current heat exchanger such as can be usedwith advantage in air conditioning. The discrete layers 6, 7 havehorizontal and vertical flutings or corrugations respectively, thecorrugations of adjacent layers having spot contact with one another andcooperating to include an angle of approximately Arrow W denotes theflow direction of the cooling water while L denotes the flow directionof the air for cooling, during operation of the system.

The regular packing member which is of square cross-section is installedin known manner in a chamber having provision for the supply and removalof air and water. The cross-section of a packing member can, of course,be e.g. circular.

Referring to FIG. 5, a packing is made up of coated layers 8 which formpart of a regular packing member for a material exchange column, e.g. arectification column, for countercurrent exchange between a liquid phaseand a gas phase. The layers or strips 8 are shown in the sequence asthey are placed seriatim one upon another, whereafter they are slideinto the material exchange section of a cylindrical column. FIG. 5 makesclear the different layer size of the individual parts, such sizesincreasing from the two outsides towards the center so that when thelayers meet, the layers result in a cylindrical member. Only four of theindividual layers are shown in detail, the remainder being showndiagrammatically.

As shown, the corrugations or the like of the adjacent layers 8 extendin such a way that the sides of the corrugations of any two adjacentlayers intersect one another.

As previously mentioned, however, the regular packing members are notlimited to the kind shown in FIGS. 4 and 5 but may also be of othershapes, e.g. of the kind having a honeycomb flow channel structure.

In order to make a regular packing member a flat structure of glassfiber bunches is wetted with an ionotropic sol and thereafter dried at atemperature of from room temperature to 300C so that the glass fiberbunches are stiffened and strengthened, for example, into the form shownin part in FIG. 3 by the resultant glass-like coating. The flatstructure may also be shaped before final drying into any suitable shapehaving walls which define discrete flow channels.

Two preparation examples will be described hereinafter for coating glassfiber woven fabrics for use as regular packing members.

PREPARATION EXAMPLES Example 1 Treatment with the following sol: 20weight parts Al (NO 9H O 400 weight parts alcohol 5 weight parts oflactic acid aluminum salt lOO weight parts of tetraethoxysilane (40% SiOThe specimens become rigid within 40 seconds at 250C. Where polar mediaare being treated, such as chlorobenzene, the two followingafter-treatments with after-drying are given after the treatment justdescribed.

lst Aftertreatment Wetting with sol of 5 weight parts zirconium acetylacetonate 90 weight parts of ethanol 1 weight parts of a molar aqueoussolution of Ti (OI- F 30 weight parts tetraethoxysilane (40% SiO Dry 2ndAftertreatment 1% aqueous solution of N -B- (amino-ethyD-yaminopropyltrimethoxysilane Example 2 Treatment of glass fiber woven fabric withthe following sol:

6 weight parts Al (NO 9 H 0 500 weight parts alcohol 114 weight partstetraethoxysilane 9 weight partsdi-isopropyloxy-titanium-bis-acetylacetonate The specimens become rigidin 3 seconds at 230C.

The invention thus provides a means of making a regular packing memberof glass fibers which is non-corrosive and temperature-resistant atleast up to 300C. The packing member is also constructed so thatcapillary action is retained between the glass fibers to ensure auniform liquid distribution in use.

The bonding agent is the coating which is chemically bonded to the basematerial of glass fibres and which simultaneously bonds at least anumber of adjacent fibres together.

The glass-forming oxide has the elementary structure of glass andcoating. The coating is formed by dis- 6 charge of the colloidalparticles of the ionotropic sol. It gives a gel and subsequently itpolymerizes into an elementary glassy structure.

What is claimed is: 1. A method of making a regular packing member formaterial exchange columns and heat exchangers, the said regular packingmember having walls defining flow channels therein, each said wallincluding a non-selfsupporting base material of glass fibers, comprisingthe steps of wetting a flat structure of said glass fibers with aglass-forming ionotropic sol consisting of charged colloidal particlesand containing at least one glass forming oxide selected from thecompounds of silicon, aluminum, zirconium, and titanium which entersinto a chemical compound with the glass fibers of the fabric layer,thereafter shaping and drying the wetted structure at a temperature of300C or less to form an irreversible stiffened packing member structure.

2. A method as set forth in claim 1 which further comprises the step ofimpregnating the stiffened packing member with a silicate-sol andthereafter drying the impregnated member.

3. A method of making a layer for a regular packing member comprisingthe steps of obtaining a flat non-self-supporting layer of glass fiberfabric defining a plurality of open loops,

wetting the fabric layer with a glass-forming ionotropic sol consistingof charged colloidal particles and containing at least one glass formingoxide selected from the compounds of silicon, aluminum, zirconium, andtitanium which enters into a chemical compound with the glass fibers ofthe fabric layer,

shaping the wetted fabric layer to form a plurality of corrugationstherein to define discrete flow channels, and

thereafter drying the shaped fabric at a temperature below 300Cinto arigid structure.

1. A METHOD OF MAKING A REGULAR PACKING MEMBER FOR MATERIAL EXCHANGECOLUMNS AND HEAT EXCHANGERS, THE SAID REGULAR PACKING MEMBER HAVINGWALLS DEFINING FLOW CHANNELS THEREIN, EACH SAID WALL INCLUDING ANON-SELF-SUPPORTING BASE MATERIAL OF GLASS FIBERS, COMPRISING THE STEPSOF WETTING A FLAT STRUCTURE OF SAID GLASS FIBERS WITH A GLASS-FORMINGIONOTROPIC SOL CONSISTING OF CHARGED COLLOIDAL PARTICLES AND CONTANINGAT LEAST ONE GLASS
 2. A method as set forth in claim 1 which furthercomprises the step of impregnating the stiffened packing member with asilicate-sol and thereafter drying the impregnated member.
 3. A methodof making a layer for a regular packing member comprising the steps ofobtaining a flat non-self-supporting layer of glass fiber fabricdefining a plurality of open loops, wetting the fabric layer with aglass-forming ionotropic sol consisting of charged colloidal particlesand containing at least one glass forming oxide selected from thecompounds of silicon, aluminum, zirconium, and titanium which entersinto a chemical compound with the glass fibers of the fabric layer,shaping the wetted fabric layer to form a plurality of corrugationstherein to define discrete flow channels, and thereafter drying theshaped fabric at a temperature below 300*C into a rigid structure.